It took me a while to do this, but once I killed the fighters going at the cargo ships, I stayed and destroyed everything else too. But after that, when you go to the asteroids, kill the remaining fighters once you arrive. I think there are about 3 waves of three or less. Once you finish off the fighters, then dock with the station (shift + D). Don't do it the other way around!
"Intensify forward firepower!!"